Compositions that include a botanical extract and their use in the methods of skin whitening or lightening as well as methods of inhibiting melanin synthesis in the skin are described.
Skin color is primarily determined by the amount of melanin in the skin. Melanin is a brown-black pigment present in the skin. Due to the dark color of the pigment, lower amounts of melanin result in lighter skin color while higher amounts result in darker skin color. Melanin is formed by the oxidation of the amino acid tyrosine to dihydroxyphenalanine in melanocytes. This reaction is catalyzed by the enzyme tyrosinase.
Excessive skin pigmentation may be caused by hormone abnormality in the human body, genetic diseases, etc., regardless of UV, or by excessive melanogenesis and melanin maldistribution due to excessive UV irradiation. A suitable amount of melanin in the skin has the positive effect of maintaining the skin healthy and absorbing UV, etc. However, excessive melanin results in negative effects, such as skin darkening and non-uniform skin color. Thus, many scientists have studied melanogenesis inhibition.
As a result of this pivotal role of tyrosinase in melanin formation, efforts to develop effective skin whitening compositions have focused on agents that inhibit the function and activity of tyrosinase. For example, compositions have been proposed that include a variety of known tyrosinase inhibitors, such as hydroquinone, vitamin C and its derivatives, kojic acid, arbutin, glutathione, cysteine, and mulberry extract, among others.
A problem with synthetic skin lighteners such as hydroquinone or kojic acid is that they may cause skin irritation or acute dermatitis. Thus, there is a continuing desire to incorporate natural sources into compositions in an attempt to address some of the undesirable aspects of synthetic products.